1. Field of the Invention
The present invention relates to a headlamp for a vehicle comprising a lighting unit for low beam irradiation.
2. Description of the Related Art
In general, a headlamp for a vehicle is constituted by a lighting unit comprising a light source and a reflector for forward reflecting light from the light source in order to carry out forward beam irradiation in a predetermined light distribution pattern.
In that case, the lighting unit for low beam irradiation is constituted such that the beam irradiation is carried out in a low beam distribution pattern having a predetermined cutoff line on an upper edge, thereby maintaining the forward visibility of a driver of a self-car while giving no glare to a driver in a car running in the opposite direction.
In the following vehicle running situation, however, there rises a problem such that a sufficient forward visibility cannot be obtained by the beam irradiation from the lighting tool unit for low beam irradiation.
More specifically, during high speed running, the driver of the self-car watches a distant road carefully for driving. In the beam irradiation in an ordinary low beam distribution pattern, however, light is not irradiated on a part provided above the height of a cutoff line thereof. Therefore, there is a problem in that the visibility of the distant road cannot be sufficiently maintained during high speed running at night.
The invention has been made in consideration of the circumstances and has an object to provide a headlamp for a vehicle comprising a lighting tool unit for low beam irradiation which can sufficiently maintain the visibility of a distant road during high speed running in a low beam irradiation state.
The invention attains the object by such a structure that a predetermined auxiliary light distribution pattern is additionally formed by using a movable shade.
More specifically, the invention provides a headlamp for a vehicle constituted to carry out beam irradiation in a low beam distribution pattern having a predetermined cutoff line on an upper edge by a lighting tool unit comprising a light source and a reflector for forward reflecting light emitted from the light source,
wherein there are provided a movable shade constituted to take a shielding position in which a part of light incident on the reflector from the light source is shielded and a shielding release position in which the shielding is released, and a shade driving device for moving the movable shade between the snieluing position and the shielding release position,
the shade driving device moves the movable shade to the shielding position at a predetermined set vehicle speed or less, and moves the movable shade to the shielding release position when the set vehicle speed is exceeded, and
beam irradiation is carried out in the low beam distribution pattern when the movable shade is set in the shielding position, and an auxiliary light distribution pattern having a cutoff line above the cutoff line of the low beam distribution pattern is added to the low beam distribution pattern to carry out the beam irradiation when the movable shade is set in the shielding release position.
The specific structure of the xe2x80x9clighting unitxe2x80x9d is not particularly restricted if it comprises a light source and a reflector for forward reflecting light emitted from the light source, and may be constituted to carry out main light distribution control by the reflector or may be constituted such that a lens is provided in front of the reflector to carry out main light distribution control by means of the lens.
Moreover, the specific structure of the xe2x80x9clight sourcexe2x80x9d is not particularly restricted, and may be the discharge light emitting section of a discharge bulb or the filament of an incandescent bulb such as a halogen bulb.
The specific structures of the xe2x80x9cmovable shadexe2x80x9d, for example, a shape and a size are not particularly restricted if it is constituted to take a shielding position and a shielding release position.
If the xe2x80x9cshielding release positionxe2x80x9d is set to be a position in which the shielding amount of light incident on the reflector from the light source can be smaller than that in the shielding position of the movable shade, a specific position thereof is not particularly restricted and it is not necessary to always set a position in which the shielding of the light incident on the reflector from the light source can be released completely.
The specific structure of the xe2x80x9cshade driving devicexe2x80x9d is not particularly restricted if it is constituted to move the movable shade between the shielding position and the shielding release position, and a solenoid or a pulse motor can be utilized, for example. Moreover, the manner of the xe2x80x9cmovementxe2x80x9d of the movable shade by the shade driving device is not particularly restricted but a rotation or a straight reciprocation can be employed, for example.
If the xe2x80x9clow beam distribution patternxe2x80x9d has a predetermined cutoff line on an upper edge, the shape of the cutoff line is not particularly restricted. Moreover, if the xe2x80x9cauxiliary light distribution patternxe2x80x9d has a cutoff line on the upper side of the cutoff line of the low beam distribution pattern, the shape of the cutoff line is not particularly restricted. Referring to the degree at which the position of the cutoff line of the xe2x80x9cauxiliary light distribution patternxe2x80x9d is set to the upper side of the cutoff line of the low beam distribution pattern, a specific value thereof is not particularly restricted.
The specific position of the xe2x80x9cpredetermined set vehicle speedxe2x80x9d is not particularly restricted and can be set to have a proper value (for example, 70 km/hr) in the range of 60 to 80 km/hr, for example.